Pump shaft sheared 1

[Lilly_29]

Hello Everybody,

A multistage centrifugal pump between bearing type, (160 M3/hr, 450 KW) undergone a failure with its shaft broken. Location point of sheared area is DE side of pump and just underneath inner of cylindrical roller bearing. clear signs of overheating found with bearing and shaft became blackish. Vibration trends before 15 days of failure event detected normal operation without any abnormal signature. Pl have a look at cross section of the broken shaft and mention your comments what type of failure mechanism indicated by these patterns. how much time it takes to develop such failure in case of lack of lubrication in a continuous operation.

 

[TugboatEng]

I don't know what you expect to learn here. Your bearing got so hot it caused the shaft to fail likely by a reducing in strength. There is nothing to read from the failure surface because it rubbed on itself and ground away any indications. We can tell the failure initiated in the bearing because there are indentations from the rollers.

 

[Doug Hunter]

I agree with Tugboat that the failure surface has rubbed away all the clues. Does the left section of the shaft have an eccentric potion on its right end?

 

[TenPenny]

Typically, when a shaft breaks right at the bearing, it's due to deflection, often from running at no flow or low flow for extended periods of time.

That's where I would start, if you can get operational history.

 

[TugboatEng]

TenPenny, see the massive amount of plastic deformation just to the right of the threads in the picture. This shaft was nearly molten when it separated.